Change occurrences of gcc to the more general cc

This is done for the sake of Yosemite, which does not have gcc, and yet
this change is also compatible with Linux.

pkgs/applications/misc/mysql-workbench/default.nix

@@ -31,7 +31,7 @@ stdenv.mkDerivation rec {
   postInstall = ''
     wrapProgram "$out/bin/mysql-workbench" \
       --prefix LD_LIBRARY_PATH : "${python}/lib" \
-      --prefix LD_LIBRARY_PATH : "$(cat ${stdenv.gcc}/nix-support/orig-gcc)/lib64" \
+      --prefix LD_LIBRARY_PATH : "$(cat ${stdenv.cc}/nix-support/orig-gcc)/lib64" \
       --prefix PATH : "${gnome_keyring}/bin" \
       --prefix PATH : "${python}/bin" \
       --set PYTHONPATH $PYTHONPATH \